Surface Stabilized Combustion (SSC) of gaseous fuel/oxidant mixtures on a permeable matrix can reduce emissions of flue gas pollutants (e.g., NOx, CO, UHC), increase radiation density, and increase thermal efficiency all of which factors are important to the design of advanced compact cost-effective radiation heating combustion devices. Through the effective utilization of SSC, radiation heat flux from the matrix surface can be increased up to 80% of the heat flux providing from 20 to 40% of the total energy released from combustion by infrared radiation. Such radiation enhancement is primarily due to surface combustion on the matrix. Based on intensive heat exchange between the combustion products and the matrix, the matrix surface is heated to high temperatures. The peak flame temperature and resulting combustion products temperature in the combustion zone is in turn reduced which reduces the combustion products NOx concentration.
The distance between the combustion zone and the matrix surface is dependent on the thermal conductivity of the gas mixture exit layer of the matrix. With the gas mixture exit layer exhibiting a relatively high thermal conductivity, the flame is located at some distance from the matrix surface. In such case, most of the energy released by combustion is carried by the combustion products. A small part of the energy released by combustion is transferred to the permeable matrix. A portion of the heat transferred to the matrix is radiated to the load and a portion is transferred back to the gas mixture and stabilizes the surface combustion.
One existing method and apparatus for the SSC of fuel/oxidant gas mixtures involves SSC on a permeable matrix consisting of particles of a heat-resistant metal alloy containing iron, chromium and aluminum. Refractory alloys containing aluminum are on the surface of the matrix. When heated in the presence of oxygen, a dense aluminum oxide film 1 micron in thickness is developed which prevents further oxidation of the surface and protects the surface from corrosion. However, such a thin film of aluminum oxide significantly affects only the chemical oxidation processes of the surface and has no significant effect on the heat exchange between the combustion products and the surface of the burner.
A device is known for the implementation of gas surface combustion on the outside surface of a sleeve of woven ceramic fibers. The sleeve is worn on a perforated metal carrier, through which the fuel/oxidant gas mixture is fed to the fabric sleeve. A disadvantage of this device is that the heating of the gas mixture while the gas mixture passes through the perforated metal carrier is insufficient to ignite (and maintain) combustion of the gas mixture. The sleeve of woven ceramic fibers substantially prevents heat transfer between the combustion products and the surface of the perforated metal carrier. Thus, an auxiliary triggering device is used to initiate (and maintain) combustion of the gas mixture over the outer surface of the woven ceramic fiber sleeve.
Another existing device burns gas on the surface of a thick layer of ceramic fibers and polymers deposited on the surface of a corrosion resistant mesh screen. The thickness of the layer of ceramic fibers and the polymers is selected to prevent corrosion heating of the mesh screen. The thickness of the layer of ceramic fibers and polymers is from 6.35 mm to 12.7 mm. A disadvantage of this device is the fact that during operation the gas mixture is preheated and burnt within the thick layer surface of ceramic fibers and polymers are burnt out and degrade.